Compression fittings are one of the most versatile fittings available. They can be used on copper pipe or plastic pipe as long as a pipe insert is used. Just out of curiosity I thought I would see just how much pressure a compression fitting could hold without failing. Surprisingly it held 50Bar, which is 725Psi, that is a huge amount of pressure. This video also proves that no sealing compound or PTFE tape is required when using compression fittings.